1. Field of the Invention
The present invention relates to a method of producing lumber products, such as square timbers and/or boards or the like, which are machined on all sides. According to this method, in a first machining phase, a trunk, which is larger toward one end and is curved in the longitudinal direction, first has one longitudinal central plane thereof which is disposed in its direction of curvature aligned in a position approximately parallel to the machining planes of two side cutting devices; the machining planes of the side cutting devices are parallel to one another, and the side cutting devices are disposed across from one another on both sides of a processing line of a machining station of a sawmill equipment. In a subsequent machining step, the trunk is flattened on two opposite longitudinal sides with the side cutting devices. Thereafter, boards which are provided with the flattened sides are cut off. The present invention also relates to an apparatus for carrying out this method. This apparatus has a conveying device for the trunk, and two side cutting devices which are disposed across from one another on both sides of the conveying device.
2. Description of the Prior Art
German Pat. No. 29 28 949 discloses a method according to which the trunk is first flattened on all sides. After that, edges, including bark, are milled or cut out, and subsequently a board exposed in this way is cut off of each side of the trunk. The remaining square portion of the trunk can be used subsequently, for example, as square timber, or can be cut up into boards.
This known method does not take into account that the trunk which is to be machined has generally grown somewhat crooked, and that one of its ends is generally considerably larger than the other end. As a rule, the increase in diameter of a trunk, measured in the direction of the larger end thereof, is 0.5 to 1.5 centimeters per meter. Depending upon the natural curve of the trunk and the respective need for cut lumber, the round timber which is to be machined or cut has a length of from 1 to 10 meters. Trunks which had grown particularly irregularly were, up to now, split up into sections having as small a curvature as possible. However, even these trunk sections still have a curvature, a so-called residual curvature.
Pursuant to another known method (German Offenlegungsschrift No. 31 14 843), only the above described taper of the trunk is taken into account. After the longitudinal sides are flattened, edges are milled or cut out by vertical movement of the trimming cutters in such a way that they form an angle relative to the horizontal.
With both of these heretofore known methods the curvature of the trunk is not taken into account during alignment and flattening. As a result, the cross-sectional area of the trunk which is actually available is not fully utilized, so that the yield from the trunk is not optimal.
Pursuant to German Auslegeschrift No. 26 05 987, in the method of the general type described at the beginning of the specification the curvature of the trunk is taken into account to the extent that after alignment the trunk is laterally flattened, is turned by 90 degrees, and is then split by a central cut along its curved center line into two equally sized blocks. These blocks are then fed for further machining to separate conveyors, block reducing stations and cutting stations. That side located across from the central cut surface is first sawed off, and a plurality of boards are subsequently cut off. The block obtained at the cutting station is curved in conformity with the curvature of the trunk, and must therefore be subsequently linearly straightened by conditioning and drying.
Not only are these post treatments expensive and time consuming, but also only can be realized to a limited extent. For example, fresh and greatly curved lumber cannot be straightened in this manner. Furthermore, the saw blades of the saws of the cutting station are very greatly stressed when carrying out the curved cuts, so that already after a relatively short time these saw blades heat up considerably and can even break. The saw chain must then be replaced, which involves considerable cost and loss of production. Finally, the apparatus required for this known method is structurally very complicated and expensive, since for transporting and machining each block half the apparatus must be equipped with a duplicate set of tools. Therefore, the apparatus also requires a relatively large amount of space.
An object of the present invention is to provide a method and apparatus of the initially mentioned general type embodied in such a way that even greatly curved trunks, in a simple manner and with as large a yield as possible, can be split up into main products and boards exclusively with straight cuts.